Cardiopulmonary resuscitation or CPR is a combination of rescue breathing (mouth-to-mouth resuscitation) and chest compressions. If a person is not breathing or circulating blood adequately, CPR can restore circulation of oxygen-rich blood to the brain and heart. CPR may be necessary during many different emergencies, including cardiac arrest, accidents, near-drowning, drug overdose, suffocation, poisoning, smoke inhalation, and electrocution injuries.
CPR involves administering a number of chest compressions, each at a specified rate and force, separated by moments of artificial respiration therebetween. When a user is performing CPR, accuracy in performing the task is important. The timing, number and force of each chest compression must be precisely executed to assure maximum effect of the procedure on the person. Furthermore, since providing CPR is usually done during times of duress, keeping track of the compressions, keeping an even rhythm, and maintaining a constant compression force can be difficult, especially for an untrained or newly certified user.